Accumulation of Extracellular Amino Acids by Euglena gracilis

Abstract

SYNOPSIS. Normal Euglena gracilis, strain z, growing in the light in defined medium (initial nitrogen concentration 140 μ/ml) depletes the medium of all ninhydrin‐positive N by the time a cell density of 2 million per ml is reached. A further 2‐ to 3‐fold increase in the cell number takes place in the absence of exogenous N. The N content of an early log phase cell is about 100 picograms but decreases very rapidly as the culture continues to grow, reaching 22 picograms in the stationary phase. When grown in the dark, normal cells take up N somewhat more slowly but the supernatant fluid from saturation cultures is again devoid of N. At modest cell densities, the permanently bleached strains examined contain less N per cell than do normal strains. The cultures of the bleached strains achieve a maximum density of about 1 to 2 million per ml rather than the 4 to 5 million reached by the normal strain. As a result, supernates from stationary phase cultures of bleached cells still contain a large proportion of the total N supplied. Paper chromatographic analysis of these supernates reveals several ninhydrin‐positive compounds. Most of these have been identified as common amino acids. Some of the properties of two unidentified, ninhydrin‐positive compounds are described.

Nitrogen Fixation by Myxophyceae from Marine Environments

“…The lower labelling of the medium shows that all the nitrogen liberated is not specifically associated with the fixation process, this suggestion being supported by the findings (Fogg, 1952;McCalla, 1963) that non-nitrogen-fixing algae also liberate extracellular nitrogen. Zelitch, Rosenblum, Burris & Wilson (1953) found that Clostridium pasteurianum liberated extracellular nitrogen more highly enriched with 15N than the intracellular nitrogen after 45 min.…”

Effect of Temperature on the Contents of the Two Energy‐Reserve Substances, Paramylon and Wax Esters, in Euglena gracilis1

“…Organism and culture. To eliminate the effect of light, a streptomycin-bleached mutant of Euglena gracilis strain Z (15) was employed. The cells were adapted to 33, 26, or 15°C by successive cultivations at these temperatures, and the adaptation was maintained by transplanting a small part of the stationary phase culture at each temperature to a new medium at the same temperature weekly for the 33 and 26°C cells and every 20 days for the 15°C cells.…”

Occurrence of Glycolate Dehydrogenase in Mitochondria and Microsomes in Streptomycin-Bleached Mutant ofEuglena gracilisz

“…The streptomycin-bleached mutant of E. gracilis z was obtained according to the method of McCalla 2 ) and was cultured in the Koren-Rutner's mediumB) in the dark. Cells reached the stationary phase of growth in about 4 days, and the cells grown for 7 days were used throughout the experiments.…”